Noise from the first 45MW IHI LM6000 gas turbine located at Bairnsdale , Australia , generated excessive noise levels when operating at loads of 20 and 30MW. At a load of 40MW the acoustically treated plant complied with the project noise level of 37dBA at a distance of 750m, but at low loads the equipment generated excessive noise levels.

A noise survey was conducted by Marshall Day Acoustics around the turbine using sound intensity techniques. The resulting survey indicated 5 major noise sources that contributed to excessive noise at the nearest affected houses. A further and complex problem was tonality, arising from the dominant100Hz tone produced by the generator. A series of practical noise control treatments on the air compressor, hydraulic starter, LPC bleed and generator enclosure was carried out, which reduced noise levels and eliminated the tonal problem.

Following the noise control works, noise levels were re-assessed at the nearest affected houses and an overall reduction of 3dBA was achieved. More importantly the tonality, which incurred a 5dBA environmental penalty on the measured levels, was reduced significantly.

This noise reduction enabled permission to be granted for the installation of a second generator to be installed at the site, which was supplied and commissioned within a 6 month period to enable power to be provided for the imminent, very heavy summer peak load.